Treatment of sour hydrocarbon distillate



P. URBAN ET AL TREATMENT OF SOUR HYDROCARBON DISTILLATE Filed Deo. 18, 1957 Jan. l2, 1960 UQ/ Summum@ `l Mil-131111.

A TTORNEYS:

United States Patent() W TREATMENT GF SOUR HYDROCARBON VDISTILLATE Peter Urban, Northbrook, and Kenneth M. Brown, Hinsdale, Ill., assignors, by mesne assignments, to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Application December 18, 1957, Serial No. 703,545

14 Claims. (Cl. 208-205) This invention relates to the treatment of sour hydrocarbon distillate and more particularly to a novel method of effecting sweetening thereof. Y

Conventional practice at the present time includes the treatment of sour hydrocarbon distillate to remove mercaptans by contacting the hydrocarbon distillate lwith an alkaline solution. -Mercaptides formed vduring this contacting are soluble in the alkaline solution, and the alkaline solution is separated from the treated distillate and subjected to regeneration. Although many attempts have been made in the past to regenerate the alkaline solution by oxidizing the mercaptides to disulfides, this process has notrattained commercial success because efficient and sufficient regeneration has not been obtained. Various modifications have been attempted but still have been unsuccessful. For example, a proposed solution of this problem has been the use of a metal chelate such as disalicylal ethylene diamino cobalt. However, this and previously suggested compounds decompose during use, with the unsatisfactory result that the catalyst is of very short life and, probably more important, the cobalt or other metal is entrained or dissolved in the treated hydrocarbon distillate. The metal in the distillate acts as a pro-oxidant to catalyze undesirable oxidation reactions, with the re* sultant formation of gums, discoloration, and other deleterious effects.

Recently it has been found that certain phthalocyanine compounds are extremely effective catalysts for oxidizing mercaptans or mercaptides and that these phthalocyanine compounds are stable during use. With this new discovery, a novel process has been developed for effecting sweetening of hydrocarbon distillates, with regeneration of the alkaline solution now being efficiently accomplished by oxidation. During oxidation of the alkaline solution, disulfides are formed, the disulfiides being dispersed through the alkaline solution. VIn accordance with the present invention the disulfides are coalesced and settled, the disuliides being separately withdrawn from the regenerated alkaline solution and the latter is reused in the process. This is an important step in the present process because a major portion of the sulfur compounds thus are removed and are not returned to the gasoline with the regenerated alkaline solution. Sulfur compounds appear to reduce the tetraethyl lead susceptibility of gasoline and, therefore, in accordance with the present invention a substantial proportion of the sulfur compounds are removed separately from the process.

`in another embodiment of the present invention the hydrocarbon distillate treated in the above manner is given a further treatment in order to produce a sweet or substantially sweet product. While the hydrocarbon distillate from the first treatment is substantially reduced in mercaptan sulfur, the distillate still contains mercaptans which are difficultly extractable. In this embodiment of the invention, a portion of the regenerated alkaline solution is contacted with the treated gasoline in the presence of air, and the mercaptans remaining in the gasoline are oxidized to disuldes, thereby producing a sweet or substantially sweet product. The finally produced disulfides remain in the gasoline but they comprise only a small 2,921,021 Patented Jan. 12, 1960 ICC proportion of the mercaptans contained in the original distillate.

From the above description it will be seen that a sweet or substantially sweet product is obtained by the novel process of the present invention. While removal of a major proportion of the mercaptans normally is readily obtained, removal of the remaining small amount of mercaptans is difficult and requires complicated and expensive treatments, such as copper treating, sodium plumbite treating, etc. These costly treating steps are avoided by the novel process of the present invention in which final sweetening is accomplished by an inexpensive oxidation treatment. As hereinbefore set forth, it is only because of the recent availability of the phthalocyanine catalyst that the improved process is attained.

The phthalocyanine catalyst is both very active and highly stable. Because of its high activity, the catalyst is used in exceedingly small concentrations. These may range from 5 to 50G and preferably l0 to 100 parts per million by Weight of the alkaline solution, although lower or higher concentrations may be used in some cases. The use of higher concentrations are unnecessary in most cases but may be used if desired, and thus may range up to 25% or more by Weight of the alkaline solution. Because of its high stability, the catalyst is used for exceedingly long periods of time. As will be shown in the following examples, caustic solution containing 5G parts per million of cobalt phthalocyanine disulfonate has been used to treat an equivalent of 30,000 barrels of gasoline and the catalyst still was very active and can be used to treat additional gasoline.

The present invention is especially suitable for the sweetening of hydrocarbon distillates and particularly sour gasoline, including cracked gasoline, straight run gasoline, or mixtures thereof, naphtha, jet fuel, kerosene, aromatic solvent, stove oil, range oil, fuel oil, etc. IOther hydrocarbon distillates include lube oil, as well as normally gaseous fractions. In still another embodiment the novel features of the present invention may be utilized for purifying other organic fractions containing certain acidic impurities. These organic compounds include alcohols, ketones, aldehydes, etc.

Any suitable alkaline solution is utilized in the process and comprises particularly sodium hydroxide (caustic), potassium hydroxide, etc. The alkaline solution generally is utilized as an aqueous solution of from about 5 to about 50% Weight concentration. When desired, solutizers, solubilizing agents, etc. are employed including, for example, alcohols and particularly methanol, ethanol, etc., phenols, cresols, butyric acid, etc., in order to increase the contact and/ or reaction of the acidic compounds with the alkaline reagent. A particularly preferred agent for this purpose is methanol and its use will be described hereinafter in further detail. in some cases the hydrocarbon distillate contains phenol compounds in sufcient concentration to serve this purpose; otherwise they may be introduced from an extraneous source.

Any suitable'phthalocyanine catalyst meeting the requirements of high activity and stability during use may be employed in the present invention. Particularly preferred metal phthalocyanines comprise cobalt phthalocyanine and vanadium phthalocyanine. The metal phthalocyanine in general, is not readily soluble in aqueous solutions and, therefore, for improved operation is preferably utilized as a derivative thereof. A particullarly preferred derivative is the sulfonated derivative.

Thus, a preferred phthalocyanine catalyst comprises cobalt phthalocyanine disulfonate. Another preferred catalyst comprises vanadium phthalocyanine disulfonate. These compounds may be obtained in the open market or may be prepared in any suitable manner as, for example, by reacting cobalt or vanadium phthalocyanine 3 with 20% fuming sulfuric acid. While the sulfonic acid derivatives are preferred, it is understood that other suitable derivatives may be employed. Other derivatives include particularly the carboxylated derivative which may be prepared, for example, by the action of trichloroaceticacid on the metal phthalocyanine or by the action v of phosgene and aluminum chloride. In the latter reaction the acid chloride is formed and may be converted to the desired carboxylated derivative by conventional hydrolysis.

The invention is further explained with reference to the accompanying flow diagrammatic drawing which illustrates several specific embodiments of the invention. It is understood that the broad scope of the present invention is not limited to the specific illustrations in the drawing.

In -the interest of simplicity the drawing will be described with reference to the sweetening of a sour gasoline with caustic solution (sodium hydroxide) containing cobalt phthalocyanine disulfonate, although it is understood that other organic compounds, other alkaline solutions and other phthalocyanine compounds may be used as hereinbefore set forth. Referring to the drawings, sour gasoline is introduced into the process through line 1 and is directed, preferably through a suitable distributing device indicated at 2, into extractor 3. When the sour gasoline contains hydrogen sulfide, it may be given a prior wash with an alkaline solution and preferably caustic solution to remove hydrogen sulde by conventional means, not illustrated. In the case here illustrated, zone 3 comprises a vertical extraction zone, which preferably contains suitable packing material and/or contacting means, including bales, side to side pans, bubble trays, bubble decks, etc. A packing material preferably also is utilized and should be one that will not be detrimentally alected by the alkaline solution and hydrocarbons at the operating conditions prevailing in this zone. A particularly suitable packing material comprises carbon Raschig rings. It is understood that two or more extraction zones may be employed and also that horizontal extraction zones may be employed.

In zone 3, the gasoline flows upwardly in initimate contact with caustic solution containing cobalt phthalocyanine disulfonate, introduced in the manner to be hereinafter set forth to zone 3 through line 4, preferably through a suitable spray arrangement illustrated at 5. When desired, fresh caustic may be introduced, or spent caustic withdrawn, by way of the extension of line 4. During contact of the gasoline with the caustic solution, acidic organic compounds, such as mercaptans and phenols contained in the gasoline, are converted into sodium mercaptides and phenolates and are dissolved in the alkaline solution. The rates of flow of the gasoline and alkaline solution are adjusted so that the treated gasoline being withdrawn from zone 3 through line 6 contains substantially less mercaptans than the sour gasoline introduced through line 1. The gasoline withdrawn through line 6, although not sweet, may be suiciently -reduced in mercaptan content to satisfy the requirements and, in this embodiment of the invention, the gasoline is withdrawn from the process through line 6 and used for any desired purpose. In another embodiment of the invention, when a sweet or substantially sweet gasoline is desired, the partly treated gasoline is subjected to further treatment in the manner to be hereinafter described in detail.

Treatment of the gasoline with caustic solution in zone 3 may be effected at any suitable temperature, which temperature is above the freezing point of the caustic solution. Generally ambient temperature is satisfactory, although in some cases lower or higher temperatures may be used, ranging from as low as about 25 up to about 220 F. Preferably temperatures of from about 80 to about 110 F. are employed. Any suitable pressure may be employed and generally is within the range of from about 25 to 200 pounds per square inch, although lower or higher pressures may be employed in some cases. Preferably superatmospheric pressure is employed in the system in order to facilitate recovery of hydrocarbons from the excess air subsequent t0 the regeneration of the caustic solution when desired.

The spent caustic solution containing cobalt phthalocyanine disulfonate and sulfur compounds is withdrawn from the lower portion of zone 3 and is directed by way of line 7, preferably through a suitable spray arrangement illustrated at 8, into regenerator 9. Air, oxygen or other suitable oxygen-containing gas is introduced into zone 9 through line 10 and preferably through a suitable spray arrangement as illustrated at 11. In regenerator 9 sodium mercaptides are oxidized to regenerate sodium hydroxide and to oxidize the sulfur components to disulfdes. Oxidation in zone 9 may be effected at any suitable temperature, which generally will be within the ranges hereinbefore set forth in connection with the description of zone 3. Excess air is withdrawn from the system through line 12 and may be reused in the process or disposed of as desired.

The regenerated caustic solution, cobalt phthalocyanine disulfonate and disulfides formed in zone 9 are withdrawn as a mixture through line 13 and, in one embodiment, are passed through line 14 into coalescer 15, preferably through a suitable spray arrangement as illustrated at I6. In another embodiment, the mixture passing through line 13 preferably is heated in any suitable manner as, for example, by being passed through heat exchanger 17 and then through lines 18 and 14 into coalescer 15. It has been found that heating of the mixture to a temperature within the range of from about to about 300 F. and preferably of from about to about 200 F. results in an over-all reduction of the total sulfur content of the treated gasoline, as will be shown by the examples appended to the present specifications. The higher temperature apparently causes further oxidation of mercaptans and at the same time consumes the oxygen entrained in the caustic solution. It is understood that any suitable heating means may be employed and conveniently comprises a heat exchanger arrangement as illustrated at 17.

As hereinbefore set forth, oxidation of the caustic solution in zone 9 results in a formation of disuldes. In order to avoid the deleterious effects of disulfides in the gasoline, it is important that the caustic solution be treated to remove the disuldes prior to recycling of the caustic solution for further use in the process. The disulfdes contained in the caustic solution being withdrawn through line 13 are in finely dispersed condition and are not readily removable. Disulde separation is accomplished in the present process by subjecting the mixture to treatment in zone 1S to coalesce the disuldes so that they may be separated from the caustic solution. Any suitable coalescing system may' be employed and preferably comprises passing the caustic-disulfide mixture through a bed of sand, straw, glass wool, etc. A particularly effective coalescing agent is prepared by coating sand with a material available on the market as Desicote which is an organo silicone chloride. The mixture then is withdrawn from zone 1S through line 19 and is passed into settling zone 20.

In zone 20 an upper disulfide layer separates from an aqueous caustic solution layer containing cobalt phthalocyanine disulfonate. The disulfides are withdrawn through line 21 and may be used for any desired purpose. The regenerated caustic solution now substantially free from' disulfide but containing cobalt phthalocyanine disulfonate is withdrawn from settler 20 through line 22 and all or a major portion thereof is recycled by way of lines `23 and 4 to extractor 3 for further use therein. While most of the disulfides are removed in the settler, in some cases the settler may be followed by a naphtha wash, not illustrated, to remove the small proportion of soluble dsulides still retained in the caustic solution. Preferably a low boiling hydrocarbon, such as pentane, hexane or mixtures thereof, is used so that the hydrocarbon may be recovered readily from the disultides and reused in the process.

From the above description it will be seen that extraction of mercaptans is effected in a manner to remove a substantial portion of the mercaptans contained in the sour gasoline and that the sulfur is converted to disuldes in the regeneration zone by oxidation in the presence of an active but stable catalyst. In this embodiment the cobalt phthalocyanine disulfonate catalyst is retained in the caustic solution and passes through the system in the manner hereinbefore set forth. Disuldes are removed from the regenerated caustic solution prior to recycling thereof and, therefore, the treated gasoline withdrawn through line 6 does not contain disuldes carried in the recycled caustic solution back into the extraction zone. As will be shown by the following examples, effective regeneration of the caustic solution is accomplished by oxidation in the presence of the cobalt phthalocyanine disulfonate catalyst and, accordingly, a regenerated caustic solution is recycled which has a high capacity to extract mercaptans from additional sour gasoline.

When desired, the treated gasoline being withdrawn from zone 3 by way of line 6 may be subjected to water wash to remove any entrained caustic solution. This is `accomplished by directing the treated gasoline through line 6 into wash zone 24, preferably through a suitable spray device illustrated at 25. In zone 24 the gasoline is passed countercurrently to a descending stream of water introduced through line 26, preferably through a distributing device illustrated at 27. Water containing caustic is removed from the lower portion of zone 24 through line 28 and may be reused, discarded or used for any other suitable purpose, while the treated gasoline is withdrawn from the upper portion of zone 24 through line 29.

As hereinbefore set forth, treatment in the manner hereinbefore described will produce a gasoline product of substantially reduced mercaptain content. However, when'a sweet or substantially sweet gasoline product is desired, the gasoline is treated further in the following manner. Inthis embodiment the gasoline withdrawn through line 6 from extractor 3 is passed through line 30 into nal treater 31, wherein it is contacted with a minor portion of the regenerated alkaline solution withdrawn through line 22 from settler 20 and directed by' way of line 32 into nal treater 31, preferably through a suitable vspray arrangement illustrated at 33. Air is introduced by way of line 34 and spray arrangement 35 into treater 31. As hereinbefore set forth the regenerated alkaline solution contains the cobalt phthalocyanine catalyst and -thus effects oxidation of remaining mercaptans which were not extracted in zone 3 but remained dissolved or entrained in the gasoline withdrawn through line 6. As an important feature of the present invention, the use of the cobalt phthalocyanine disulfonate catalyst, being both an active oxidation catalyst and stable under the conditions of use, effects substantially complete oxidation of the mercaptan compounds and thereby produces a sweet or substantially sweet final product. Preferably `the amount of air employed at this stage is just sufficient to react with the mercaptans still contained in the gasoline introduced into zone 3l. Sweetening in Zone 31 is effected under substantially the same temperature and pressure as utilized in zone 3. The treated gasoline is withdrawn from zone 31 through line 35 and may be removed from the process through line 37 or water washed by being directed through line 6 into Zone 24 in the manner heretofore described. The caustic solution is withdrawn from zone 31 through line 38 and preferably is directed by way of line 7 into zone 9 for regeneration and reuse in the manner heretofore described.

In general it s preferred to eiect the final treatment in a zone separate from extractor 3. However, in another embodiment of the invention, the inal treatment may be effected in the upper portion of extractor 3 and in an open communication therewith. In this embodiment the lesser quantity of air is introduced into an upper portion of the extraction zone in order to effect final sweetening of the ascending gasoline. The air is introduced below the introduction of the regenerated caustic solution which, in this embodiment of the invention, is introduced near the top of extractor 3.

From the above description it will be seen that the recent availability of the phthalocyanine catalyst permits the new process herein described. This results in a considerably improved process over those of the prior art. Although the disuldes formed in Zone 31 will be retained in the gasoline, these comprise only a minor proportion of the sulfur compounds originally contained in the sour gasoline charged to the process through line 1. As hereinbefore set forth, this process offers numerous advantages over the more complicated and costly methods required in the past to produce a sweet gasoline, such as copper treating, etc.

As hereinbefore set forth, still further improved results are obtained when a solutizer is used. The solutizer serves to increase solubility of the mercaptans in the caustic solution and thereby enhances conversion and extraction of mercaptans. A particularly preferred solutizer is methanol. However, for an economical commercial process, it is important to prevent loss of methanol from the process. The drawing illustrates one method of recovering the methanol which is dissolved in the treated gasoline and/or entrained in the excess air stream. In this embodiment the treated gasoline is directed from either zone 3 or zone 31 by way of line 6 into wash zone 24, where it is countercurrently contacted with Water in the manner heretofore described. Similarly excess air from regenerator 9 is directed by way of lines 12 and 39 into wash zone 40, preferably through a suitable spray arrangement illustrated at 41. Water is introduced into zone 40 by way of line '42 and preferably through spray arrangement illustrated at 43. In a preferred embodiment, water containing methanol is withdrawn from zone 40 through line 44 and commingled with the water withdrawn from zone 24 by way of line 28 and, while all or a portion may be removed from the process by Way of line 45, at least a portion is directed through line 46 into methanol fractionator 47. Excess air is removed from zone 40 through line 64.

In zone 47 the methanol-water stream is subjected to heating and distillation by any suitable means such as reboiler 4S or in any other suitable manner. In zone 47 methanol is separated from water, and the latter is removed therefrom through line 49. A portion of the water is directed by way of line 50 into and through reboiler 48 and returned by way of line 51 to fractionator 47. The water withdrawn through line 49 may be removed, in part, from the system through line 52 but preferably is recycled through line 53 to wash zones 24 and/or 4t). Additional water, when required, may be introduced into the system through line 52. Methanol is removed from the upper portion of zone 47 through line 54 and directed into and through condenser 55 and line 56 to receiver 57, having conventional gas release line 5S. Methanol is withdrawn from receiver 57 through line 59, a portion being recycled by way of line 60 to the upper portion of zone 47 to serve as a cooling and refluxing medium therein. The remaining portion of the methanol is directed by way of line 61 and, while all or a portion may be withdrawn from the process through line 62, preferably at least a portion of the methanol is directed through line 63 and returned by way of lines 23 and 4 to extractor 3. When desired, the methanol may be introduced into extractor 3 at a point beneath the introduction of the caustic solution.

This has the advantage of using the caustic solution to extract methanol which may be entrained in the ascending gasoline.

In a preferred embodiment the phthalocyanine catalyst is dissolved in the caustic solution and circulates through the process in the manner heretofore described. In another embodiment the phthalocyanine catalyst may be used as a solid bed of catalyst, preferably the phthalocyanine catalyst being composited with a suitable solid carrier and particularly charcoal. Any suitable charcoal may be employed, including bone char, wood charcoal, charcoal made from coconut or other nut shells, fruit pits, etc. Other carriers may be employed as, for example, alumina, silica, etc. In this embodiment xed beds of the phthalocyanine catalyst are disposed in regenerator 9 and, when employed7 in iinal treater 31. Thus regeneration of the caustic solution is elected in the presence of the phthalocyanine catalyst and also inal oxidation of mercaptans is effected in the presence of the catalyst.

In the interest of simplicity, pumps, compressors, valves and other appurtenances have been omitted from the drawing. It is understood that these will be provided as required and also that heat exchangers, heaters, etc. will be provided when elevated temperatures are employed in the various steps of the process and also cool.- ers or condensers as may be required.

From the above description it will be noted that an improved process for treating sour hydrocarbon distillate is provided. As hereinbefore set forth, a sweet or substantially sweet gasoline is readily produced Without the necessity of resorting to complicated and costly methods of the prior art such as copper treating, etc. Also', the process permits regeneration of the alkaline solution by oxidation, which avoids the high temperatures required in the prior art methods of high temperature hydrolysis which, in turn, has the disadvantage of adversely affecting plant equipment and requiring cornparatively frequent replacement thereof. The improved process of the present invention is attainable only because of the recent availability of the phthalocyanine catalyst which is both an active oxidation catalyst and is stable under the conditions used in the process. Without such a catalyst, satisfactory regeneration of the caustic solution is not obtained. Furthermore, the gasoline product does not contain metal components resulting from decomposition of the catalyst during use. As will -be shown in the examples appended to the present specications, cobalt phthalocyanine disulfonate has been used for an extensive period of time and, to the limit of present analytical methods, shows no change in composition or activity. Furthermore, the gasoline products are free from cobalt which further coniirrns the high stability of the cobalt phthalocyanine disulfonate catalyst.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

Example I The gasoline used in this example was a cracked gasoline having a total sulfur content of 0.096% by weight and a mercaptan sulfur of 0.0457% by weight. The gasoline was treated with a refinery caustic solution of about 10% by weight concentration. In a continuous laboratory treatment, 1200 cc. per hour of the gasoline was charged. 150 cc. of the 10% by weight caustic solution containing 5 0 parts per million by weight of cobalt phthalocyanine disulfonate was utilized. The extraction was effected at room temperature. The treated gasoline removed from the extractor had a mercaptan sulfur content of 0.0117% by weight. This high mercaptan content apparently resulted because the more difliculty oxidized mercaptans were recycled in the caustic solution and then dissolved in the gasoline. However, in other runs, the mercaptan content of the treated gasoline was reduced to about 0.003%. The caustic solution containing cobalt phthalocyanine disulfonate was regenerated at room temperature by contacting with 700 cc. of air per hour. The regenerated caustic solution contained disuldes dispersed therein and was coalesced at room temperature by being passed through a bed of Desicote treated sand and then passed into a settler. A disulfide layer was removed from the upper portion of the settler and a regenerated caustic solution containing cobalt phthalocyanine disulfonate was removed from the lower portion of the settler. A major portion by volume) of the regenerated caustic solution containing the phthalocyanine catalyst was recycled for further use in the extraction zone. A minor portion (20% by volume) of the regenerated caustic solution containing cobalt phthalocyanine disulfonate was contacted with the partially treated gasoline and air was introduced into the iinal treating zone at a rate of 70 cc. per hour. The gasoline withdrawn from the final treater was doctor sweet.

Example II The caustic solution containing cobalt phthalocyanine was used in the above and in many other runs to treat 99 kg. of gasoline. The total phthalocyanine catalyst inventory was 10 mg. and the plant inventory of caustic was 200 gm. This is the caustic originally charged. Thus, it is seen that the novel process of the present invention permits extensive use of the caustic. Computed on a commercial scale, an equivalent of one pound of cobalt phthalocyanine disulfonate catalyst is used to treat approximately 9,820,000 pounds of gasoline or approximately 30,000 barrels of gasoline. As hereinbefore set forth, the caustic solution still is usable for treating additional gasoline. No change in activity or composition of the cobalt phthalocyanine disulfonate was detected. The treated gasoline was analyzed and contained no detectable amounts of cobalt.

From the above data it will be seen that a considerably improved process is presented. The caustic solution and catalyst have been used to treat an equivalent of over 30,000 barrels of gasoline and still may be used to treat additional quantities of gasoline. In all cases using the nal treater, a sweet gasoline was obtained.

Example III The gasoline described in Example I contained a total sulfur content of 0.096% by weight. Of this 0.045% by weight is mercaptan sulfur and the remaining 0.051% is non-extractable disulfide or other sulfur compounds. These other sulfur compounds are of a form which cannot be removed in any extraction or low temperature process. In the present and corresponding prior art processes such sulfur compounds remain in the gasoline, but are suiiciently low and the gasoline is sweet so that the gasoline normally meets commercial requirements.

However, the total sulfur content of the gasoline may be even further reduced by employing the feature of heating the regenerated alkaline solution prior to treatment in the coalescer. In a run similar to that described in Example I, except that the regenerated caustic containing disuldes and phthalocyanine catalyst was heated to a temperature of F. in several runs and 200 F. in several other runs, the total sulfur content of the gasoline was reduced to 0.069% and 0.053 It will be noted that the latter reduction is substantially equal to the nonextractable or oxidizable sulfur compounds contained in the gasoline and that practically complete removal of mercaptans is obtained.

on charcoal and utilized as a fixed bed in the regenerator. The sour kerosene contains .01% by weight of mercaptan sulfur and is subjected to countercurrent extraction with 20% potassium hydroxide solution at ambient temperature. The treated kerosene is withdrawn from the upper portion of the extractor'and now has a mercaptan content of 0.001% by weight. The potassium hydroxide solution is regenerated by blowing with air at ambient temperature in a regeneration zone containing the iixed bed of vanadium phthalocyanine catalyst. The regenerated potassium hydroxide solution is heated to 210 F. and the disuldes coalesced by being passed downwardly through a bed of sand. The coalesced mixture then is passed to a settler, wherefrom an upper disulide layer is removed. The regenerated potassium hydroxide solution is withdrawn from the lower portion of the settler and is recycle to the extractor for further use therein in extracting sour kerosene.

We claim as our invention:

1. A treating process which comprises contacting sour hydrocarbon distillate with an alkaline solution in an extraction zone, separately withdrawing therefrom a hydrocarbon distillate reduced in mercaptan content and an alkaline solution containing sulfur compounds, contacting the last mentioned alkaline solution with an oxygen-containing gas in the presence of a phthalocyanine catalyst to substantially completely regenerate the alkaline solution and to oxidize the sulfur components to disuldes in a regeneration zone, withdrawing therefrom regenerated alkaline solution containing inely dispersed disuliides and passing the mixture through a bed of coalescing agent and then into a settling zone, separating the mixture in the settling zone into a disulfide phase and an alkaline solution phase, separately withdrawing each phase, and returning at least a major portion of the seprated alkaline solution to said extraction zone for further use therein to extract mercaptans from sour hydrocarbon distillate.

2. The process of claim 1 further characterized in that said phthalocyanine catalyst is cobalt phthalocyanine disulfonate and is dissolved in and is circulated with the alkaline solution.

3. The process of claim 1 further characterized in that said phthalocyanine catalyst is vanadium phthalocyanine disulfonate and is dissolved in and is circulated with the alkaline solution.

4. The process of claim 2 further characterized in that said phthalocyanine catalyst is maintained as a solid bed in the regeneration zone.

5. A treating process which comprises contacting sour hydrocarbon distillate with an alkaline solution in an extraction zone, separately withdrawing therefrom a hydrocarbon distillate reduced in mercaptan content and an alkaline solution containing sulfur compounds, contacting the last mentioned alkaline solution with an oxygen-containing gas in the presence of a phthalocyanine catalyst to substantially completely regenerate the alkaline solution and to oxidize the sulfur components to disuldes in a regeneration zone, withdrawing therefrom regenerated alkaline solution containing iinely dispersed disuliides and passing the mixture through -a bed of coalescing agent and then into a settling zone, separating the mixture in the settling zone into a disulfide phase and an alkaline solution phase, separately withdrawing each phase, returning a major portion of the separated alkaline solution to said extraction zone vfor further use therein to extract mercaptans from sour hydrocarbon distillate, passing a minor portion of said separated alkaline solution to contact with said hydrocarbon distillate reduced in mercaptan content and introducing an oxygen-containing gas thereto to elect oxidation of mercaptans contained in said distillate and to produce a sweet hydrocarbon distillate, and separately recovering said sweet hydrocarbon distillate.

6. The process of claim 5 further`characterized in that said contacting of the sour hydrocarbon distillate with alkaline solution and said regeneration are eiected at substantially ambient temperature, and further characterized in that the regenerated alkaline solution containing disulfdes is heated to a temperature of from about to about 300 F. prior to passing into said bed of coalescing agent.

7. The process of claim 6 further characterized in that said regenerated alkaline solution is heated to a temperature of from about to about 200 F.

8. A continuous regenerative sweetening process which comprises countercurrently contacting sour gasoline with caustic solution in an extraction zone, separately withdrawing therefrom a partly treated gasoline and a used caustic solution containing sulfur compounds, substantially completely regenerating the used caustic solution by oxidizing with air in the presence of a phthalocyanine catalyst and at the same time oxidizing sulfur components to disuldes in a regeneration Zone, withdrawing therefrom the regenerated caustic solution containing finely dispersed disuldes and passing the mixture through a bed of coalescing agent and then into a settling zone, separating the mixture in the settling zone into a disulfide phase and a caustic solution phase, separately withdrawing each phase, returning a major portion of the separated caustic solution to said extraction zone for further use therein to extract mercaptans from sour gasoline, and passing a minor portion of said separated caustic solution to contact with said partly treated gasoline and introducing air thereto to effect oxidation of mercaptans remaining in said gasoline and to produce a sweet gasoline, and separately recovering said sweet gasoline.

9. The process of claim 8 further characterized in that said phthalocyanine catalyst is cobalt phthalocyanine disulfonate and is dissolved in and is circulated with the caustic solution.

l0. The process of claim 8 further characterized in that said phthalocyanine catalyst is vanadium phthalocyanine disulfonate and is `dissolved in and is circulated with the caustic solution.

11. The process of claim 8 further characterized in that said contacting of the sour gasoline with the caustic solution and said regeneration of the used caustic solution are eiected at ambient temperature and further characterized in that said regenerated caustic solution is heated to a temperature of from about 100 to about 200 F. prior to passing to said bed of coalescing agent.

l2. The process of claim 8 further characterized in that said caustic solution also contains methanol and that the sweet gasoline product is countercurrently contacted with water to recover methanol carried in said gasoline, the water-methanol recovered therefrom being fractionated to separate methanol from the water, and each is separately recycled within the process for further use therein.

13. The process of claim 8 further characterized in that said caustic solution also contains methanol and that the excess air from said regeneration zone is countercurrently contacted with water to recover methanol carried in said air, the water-methanol recovered therefrom being fractionated to separate methanol from the water, and each is separately recycled within the process for further use therein.

14. The process of claim 8 further characterized in that said caustic solution also contains methanol and that the sweet gasoline product and excess air are each separately countercurrently contacted with water to recover methanol carried in said gasoline and air, the water-methanol recovered therefrom being fractionated to separate methanol from the water, and each is separately recycled within the process for further use therein.

References Cited in the tile of this patent UNITED STATES PATENTS 1,998,863 lChaney et al. Apr. 23, 1935' 2,550,091 Seebold Apr. 24, 1951 2,651,595 Moulthrop Sept. 8, 1953 2,659,691 Gislon et al. Nov. 17, 1953 

1. A TREATING PROCESS WHICH COMPRISES CONTACTING SOUR HYDROCARBON DISTILLATE WITH AN ALKALINE SOLUTION IN AN EXTRACTION ZONE, SEPARATELY WITHDRAWING THEREFROM A HYDROCARBON DISTILLATE REDUCED IN MERCAPTAN CONTENT AND AN ALKALINE SOLUTION CONTAINING SULFUR COMPOUNDS, CONTACTING THE LAST MENTIONED ALKALINE SOLUTION WITH AN OXYGEN-CONTAINING GAS IN THE PRESENCE OF A PHTHALOCYANINE CATALYST TO SUBSTANTIALLY COMPLETELY REGENERATE THE ALKALINE SOLUTION AND TO OXIDIZE THE SULFUR COMPONENTS TO DISULFIDES IN A REGENERATION ZONE, WITHDRAWING THEREFROM REGENERATED ALKALINE SOLUTION CONTAINING FINELY DISPERSED DISULFIDES AND PASSING THE MIXTURE THROUGH A BED OF COALESCING AGENT AND THEN INTO A SETTLING ZONE, SEPARATING THE MIXTURE IN THE SETTLING ZONE INTO A DISULFIDE PHASE AND AN ALKALINE SOLUTION PHASE, SEPARATELY WITHDRAWING EACH PHASE, AND RETURNING AT LEAST A MAJOR PORTION OF THE SEPRATED ALKALINE SOLUTION TO SAID EXTRACTION ZONE FOR FURTHER USE THEREIN TO EXTRACT MERCAPTANS FROM SOUR HYDROCARBON DISTILLATE. 